More Powerful Telescopes on Horizon

Oct. 4

By Lee Dye

Astronomers are never satisfied.

It isn’t enough to study objects in the distant sky that are so faint they elude even the most powerful telescopes in the world. It just keeps their juices flowing, making them yearn for bigger and better instruments.

In a typically ambitious fashion, a group of astronomers have proposed building a telescope 10 times more powerful than each of the twin Keck Telescopes on Mauna Kea in Hawaii, the current global leaders.

The Dream Machine

This monster would have a primary mirror 30-meters (nearly 100 feet) in diameter, compared to the Kecks’ 10-meter mirrors, and it would have such high resolving power that it might even be able to directly detect planets around other stars. It would have the latest in adaptive optics that would remove distortion caused by the Earth’s atmosphere.

The cost? At least half-billion bucks, and these folks don’t know where that money would come from.

It sounds like the kind of bold dream that could easily be dismissed as the fanciful thinking of a few would-be visionaries, except for one thing. These are the same people who created the Kecks, and a lot of folks thought they couldn’t do that, either.

The California Extremely Large Telescope (CELT) is in the early planning stages at the University of California and the California Institute of Technology, the partnership that conceived, designed, built and operates the Keck Observatories on Mauna Kea.

Like the Kecks, the primary mirror would be an array of individual hexagonal mirrors that would be so precisely controlled they would each act as single mirrors. Each keck uses 36 segments. The new monster would use 1,080 segments.

The Kecks also use a deformable mirror separate from the primary mirror to remove atmospheric distortion, a technology called “adaptive optics.” The Keck systems use 250 tiny pistons, called actuators, to control the mirror’s shape, flexing it back and forth ever so slightly to offset any distortion caused by the air above the telescope. The new adaptive optics system would need about 5,000 actuators, and that’s beyond the capability of current technology, according to Jerry Nelson of the University of California, Santa Cruz.

It’s partly Nelson’s job to determine how that can be done. He’ll probably figure it out. The Kecks, after all, were his brainchild.

Europeans Aim Higher

A few years ago, after the first Keck began collecting light, I spent several days with Nelson, climbing around the innards of that technological marvel. He said then there was no limit to the size of a telescope that could be built based upon the multiple mirror concept, and now he and his colleagues have set out to prove it.

But as bold as the new plan is, it’s modest compared a possible 100-meter telescope that is being considered by the European Southern Observatory, based in Germany. And don’t you just love it? They call that one the OWL, for Overwhelmingly Large telescope.

It would use the segmented mirror technology, but Nelson thinks the Europeans are reaching a bit too far too quickly. It isn’t possible to just scale up the Keck to such a large beast. New technology will have to evolve, and bigger does not necessarily mean better, as the Soviets learned a couple of decades ago when they built the world’s largest telescope that turned out to be largely ineffective.